There are many known techniques for adding vulcanization accelerators to rubber so as to shorten the vulcanization time, lower the vulcanization temperature, improve various characteristics of the vulcanized rubber article and to improve the handling ability of the rubber during processing.
Vulcanization, or curing, is a term applied to the process where elastomers, natural and synthetic, are treated with certain chemicals to improve their strength and durability. In general, vulcanization will effect the following changes in raw elastomers: increase tensile strength, eliminate tackiness, decrease solubility in various solvents, increase elasticity and decrease temperature sensitivity. These improved properties can be obtained by treating the raw elastomer with sulfur in the presence of other chemicals such as accelerators. It is known that the presence of accelerators in the vulcanization process is desirable since accelerators enable the vulcanization reaction to be carried out in a shorter period of time and at a lower temperature. In some cases, vulcanization can be effected at room temperature, and the amount of sulfur may be reduced when an accelerator is incorporated into the vulcanization mixture.
If large amounts of accelerators are used in the vulcanization process, the resulting composition contains appreciable amounts of the accelerator or decomposition products thereof. Although the presence of appreciable amounts of accelerators in the final composition is not usually detrimental, there are applications where the presence of the accelerator is undesirable, for example, accelerators such as the thiazoles, are skin irritants. Thus, consideration of the amount and type of accelerator present in the vulcanized composition is important where the vulcanized composition is to be used in the preparation of fabrics and articles which may come in contact with the skin.
Vulcanization accelerators presently used in the industry also present other problems. For example, dithioacid salts such as dithiocarbamates or thiurams, so called "ultra accelerators", rapidly accelerate vulcanization at conventional vulcanization temperatures but have the problem of permaturely vulcanizing the rubber compositions during processing steps such as mixing or molding due to the heat generated by their own activity, resulting in undesired scorching of the rubber. Sulfenamides, so called "delayed action accelerators", do not possess scorching problems, but they tend to retard the rate of vulcanization.
Accordingly, it has become important in the rubber industry to find novel accelerator systems that prevent scorching of the rubber at processing temperatures, but that allow vulcanization to take place rapidly at vulcanization temperatures and to provide final compositions which do not have accelerators bloom, or come to the surface, of the rubber article.
U.S. Pat. No. 3,989,643 discloses zinc oxide and fatty acids commonly employed as accelerator activators added to the rubber in the form of a dispersion of the zinc salt of the fatty acid in an alkylphenoxy polyglycol. U.S. Pat. No. 3,989,643 teaches that such an activator system improves compounding, and mixing is completed in a shorter time and at lower mixing temperatures than when zinc oxide and fatty acid are added separately. U.S. Pat. No. 3,989,643 does not suggest or disclose that polyethoxylated moieties can be chemically bound to a polymeric material and continue to evidence enhanced cure rates.
Canadian Pat. No. 900,649 teaches that copolymers of tetrafluoroethylene and certain .alpha.-olefins or alkylvinyl ethers can be provided with optimum cure rates by copolymerizing them with from 0.5 to 5 percent by weight of an aryloxyalkylvinyl ether monomer. This patent teaches that acid cures can be enhanced through the use of such tetrafluoroethylene polymers.
Daiichi, Chem. Abs. 95:188996T discloses that nonionic surfactants having hydroxyl groups can be reacted with .alpha.,.beta.-unsaturated monocarboxylic acids in the presence of H.sub.2 SO.sub.4 to prepare polymerizable surfactants.
A Russian reference by A. G. Fomin et al, International Polymer Science & Technology, 8(7) T 54 (1980) teaches the use of carbowax polyethyleneglycols to increase cure rates in NBR.
The prior art does not suggest or disclose that polymer bound nonionic surfactants will activate sulfur cure rates and provide other benefits over the nonbound species. Further, the art does not suggest or disclose the enhanced cure rates that can be achieved for styrene/butadiene rubbers through the use of a polymeric cure activator.